In principle, a multitude of platforms for different types of balances are known whose shapes are often adapted to the respective field of application, to the weighing object and/or to the balance being used. A platform in the present context means not only a weighing platform or weighing pan that is in contact with a force-measuring system of the balance, but it also encompasses a transfer platform or support device for transporting the weighing object to and from the weighing platform. Platforms of this kind carry weighing objects during the weighing itself or during the transfer to or from the weighing platform. The cooperation between a weighing platform and a transfer platform is used for example in a weighing lift for a balance that is capable of automation.
The requirements on the design of the balance and also of the platform are increasing constantly, in particular in fields of application that are subject to stringent legal guidelines such as for example the fields of medicine, biochemistry or pharmaceuticals. These requirements include for example that the parts of the balance coming into contact with a weighing object, in particular the platform, must be easy to clean. For the cleaning, the platform is normally uninstalled from the balance, cleaned and dried separately, and then reinstalled. The objective is to not only decontaminate and clean the platform physically and/or chemically of residues, but also to sterilize it if applicable, so that it satisfies at least the legally mandated sanitary standards.
The manual or automated uninstalling and reinstalling of the platform, in particular of the weighing platform, can present problems especially in balances of very high resolution, so-called microbalances, because even an unintentional misaligning of the weighing platform in the process of uninstalling or uninstalling can cause damage to the weighing mechanism.
The desired easy cleaning of a platform thus entails the requirement that the platform be simple and problem-free to remove from and reinstall in a balance. Of course, an exchange of the platform should be possible without a loss in quality relative to the weighing result, i.e. neither the platform nor the weighing mechanism should be influenced or damaged in the process.
In JP 2006-046912 A, a saucer-shaped weighing pan is disclosed which by way of a stem attached in the direction of the load can be inserted into a holder that is in contact with the weighing cell. The stem has two resilient elements equipped with means of engagement at their free ends. For insertion into the holder, the resilient elements are pressed together. When the pressure is taken off the resilient elements, they spread apart again and push the stem into the holder. In addition, the means of engagement of the weighing pan snap into recesses in the holder so as to lock the weighing pan in place. To release the connection, the means of engagement, which protrude from the holder, are slightly squeezed together. Weighing pans of this kind can be used only if the holder is accessible in as well as against the direction of the load. This condition is not normally met in microbalances or weighing lifts of a compact design. Besides, the process of milling the weighing pan out of a block of material would be time-consuming and expensive, in particular since the resilient elements must be sturdy in order to allow the weighing pan to be exchanged regularly, and as a consequence the weight of the weighing pan can be relatively high.
Platforms of the known state of the art, particularly those that are used in balances that are capable of automation, normally consist of a plurality of parts, so that it is hardly possible to manufacture a completely gap-free platform. This has in addition to high manufacturing costs the further disadvantage that the platform needs to be dried for a very long time after a cleaning in order to ensure that all residues of cleaning liquids have been driven out of the gaps. This is necessary because in microbalances even the smallest quantities, including possible residues, are being measured and can falsify the measuring result. In addition, these platforms are relatively susceptible to wrongly directed mechanical forces and have to be handled very carefully.
Accordingly, the task presents itself to provide a platform for electronic balances, in particular for balances capable of automation, which is easy to clean and simple to exchange.